Heart muscle, light micrograph
Heart muscle. Light micrograph of a section through heart (cardiac) muscle tissue, showing cardiomyocyte muscle cells. These cells have a centrally located nucleus and are branched and joined end-to-end by special intercellular connections called intercalated discs. These discs contain gap junctions allowing conduction of electrical impulses between very many cells enabling rapid and coordinated muscle contraction. The energy needed to maintain continuous heart contraction is provided by the thousands of mitochondria in each cell, seen as dark purple streaks throughout the cytoplasm. Connective tissue between cardiomyocytes has a rich supply of blood vessels. Magnification: x556, when printed 10 centimetres high.
© MICROSCAPE/SCIENCE PHOTO LIBRARY
Moth larva's interior, SEM
Moth larva's interior. Scanning electron micrograph (SEM) of the trachea and Malpighian tubules of a moth larva (order Lepidoptera). Oxygen enters the tracheal tubes (yellow) from the spiracles (breathing pores, not seen) on the larva's body surface. The oxygen diffuses directly into the moth's cells across the branching tracheal tubes. The Malpighian tubules (pink) act like human kidneys and selectively extract metabolic waste products (water, salts and uric acid) from the circulating body fluid called haemolymph. The tubules empty into the hindgut (not seen) and the waste is expelled from the body.
© SUSUMU NISHINAGA/SCIENCE PHOTO LIBRARY
Kidney podocyte cells, SEM
Kidney podocyte cells. Coloured scanning electron micrograph (SEM) of podocyte cells on the surface of a kidney glomerulus. Podocytes possess branching, foot-like processes (red/brown). The processes from adjacent podocytes interweave, forming narrow slits that cover the glomerular membrane. The glomerulus is a tight ball of capillaries (small blood vessels) that filters the blood. Fluid is filtered from the blood as it passes through the slits formed by the podocytes into the cavity of the surrounding Bowman's capsule (not seen). After the reabsorption of certain substances, the fluid is transported to the bladder as urine. Magnification unknown.
© STEVE GSCHMEISSNER/SCIENCE PHOTO LIBRARY